KR101878456B1 - High Strength Car Underbody - Google Patents

Abstract

The present invention relates to an underbody for a high rigidity vehicle having a structure in which a skin layer and a flame-retardant layer are laminated, the skin layer comprising thermoplastic fibers having a shape-retaining function; And PETG low melting point binder and having a weight ratio of 4: 6 to 9: 1, wherein the flame retardant layer is a reinforcing fiber; And a thermosetting binder including a flame retardant, and having a weight ratio of 100 to 10 to 50. The present invention relates to an underbody for a highly rigid vehicle.

Description

{High Strength Car Underbody}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a vehicle underbody having excellent rigidity, and more particularly, to an underbody using a fiber aggregate produced by using glycol-modified polyethylene terephthalate glycoll-modified (PETG) as a binder.

The underbody mounted on the lower end of the automobile is a portion exposed to the outermost surface, so as to attenuate the air resistance caused by the collision between the vehicle body and the air during driving, to block the foreign matter generated from the ground from entering the vehicle, It protects important parts such as transmission from being damaged by friction with the road surface.

Steel is generally used as an underbody material, but the body is heavy and the friction noise with foreign substances is large, and it is a tendency to use GMT (Glass Fiber Mat Thermoplastics) recently. However, GMT is excellent in light weight and durability, but the work environment of the worker is poor due to the fine dust generated when assembling the finished product of the automobile, and there is a limit to absorb noise such as engine exhaust noise and road surface noise.

In general, it is hard to find a case where a single material such as GMT is applied to an underbody for automobiles

Therefore, various materials such as impact resistant polypropylene (PP) sheet, GMT, wet process or dry process low specific gravity glass fiber composite material are widely used for the underbody of automotive exterior parts.

Among them, polypropylene (PP) sheet is not widely applied due to its weak impact strength compared to other materials. In Korea, glass fiber mat thermoplastics (GMT), which improves the flowability of resin, are mainly used, It is difficult to form the product to a thickness of 1.8 mm or less due to the restriction of the weight, so there is a limitation in weight saving

In addition, due to the characteristics of flow molding, there is a disadvantage that the glass fiber content is small at the side portion of the product and the impact strength is low due to high distribution of the staple fibers.

Finally, in overseas countries, low specific gravity composite materials, which are lighter than GMT materials and have excellent sound absorption performance, have been used. However, this material also needs to be improved in physical properties due to its weak impact strength. In particular, There is a problem such as product breakage due to the torque of the assembling tool when the drilling process or the product is assembled to the partner water.

In addition, when the thermoplastic fiber and the low melting point binder are mixed with each other, the fiber can be used as a reinforcing fiber because it can be lightened and has excellent sound absorption properties. Therefore, there is a room for improving the sound absorption property. However, The strength of the underbody finished product is limited.

Korean National Publication No. 2013-0137811 relates to a vehicle underbody which is made of a thin plate type thermoplastic composite material including continuous fibers and can adjust the thickness of the product, thereby increasing the degree of freedom in designing, reducing weight, However, there is no description about improvement of physical properties using PETG fiber.

Korean Unexamined Patent Publication No. 2011-0125889 discloses a nonwoven fabric having excellent resilience and shape restoring ability and a cushioning material using the same. The polyester nonwoven fabric has elastic recovery ability using two or more polyesters having different heat shrinkability and has tensile strength, There is no description about the improvement of the physical properties.

Therefore, it is necessary to develop an underbody body for a vehicle which is composed of specific thermoplastic fibers and has high strength.

An object of the present invention is to provide a vehicle underbody having excellent rigidity by using a skin layer which is a nonwoven fabric using PETG fibers as a binder.

Another object of the present invention is to provide a vehicle underbody which is capable of tightly bonding fiber-reinforced PETG fibers by high-pressure welding, thereby improving adhesiveness and high strength properties.

Another object of the present invention is to provide a vehicle underbody in which a flame retardant layer is an essential component so as to protect the skin layer from heat generated in the engine of an automobile.

In order to solve the above-mentioned problems, the present invention provides a high rigidity underbody for a vehicle having a structure in which a skin layer and a flame retardant layer are laminated, wherein the skin layer comprises thermoplastic fibers having a shape-retaining function; And PETG low melting point binder, and having a weight ratio of 4: 6 to 9: 1, wherein the flame retardant layer is a reinforcing fiber; And a thermosetting binder containing a flame retardant, and provides a high rigidity underbody for a car having a weight ratio of 100 to 10 to 50.

Further, the present invention provides a highly rigid underbody for a vehicle characterized in that the thermoplastic fiber of the shape-retaining function is a thermoplastic fiber aggregate composed of at least one fiber of polyester, polyimide, fiber and acrylic and nylon resin .

In the present invention, the PETG low melting point binder is any one of a sheath core composite fiber composed of a PETG resin or a PETG resin single fiber having a sheath portion, the interfiber fusion occurs at 130 to 200 DEG C, It provides a high rigid vehicle underbody characterized by short fibers of ~ 80mm.

In the present invention, the reinforcing fiber is a fiber composed of at least one of polyphenylene sulfide, polytetrafluoroethylene, polyimide, meta-aramid, para-aramid, polyarylate and polyparaphenylenebenzobisoxazole, Wherein the fiber has a fineness of 2 to 15 denier and a length of 20 to 80 mm.

According to the present invention, PETG fibers are characterized by excellent tensile strength, flexural strength and flexural modulus using a skin layer which is a nonwoven fabric composed of a binder.

In addition, the present invention is capable of tightly bonding fibers by using high pressure fusion of PETG fibers, and is characterized in that adhesiveness and high strength properties are improved by using the PETG fibers.

Further, the present invention is characterized in that a flame-retardant layer laminated on a skin layer is provided as an essential component, so that a skin layer can be protected from heat generated in an automobile engine.

1 is a conceptual diagram of a highly rigid underbody section for a vehicle according to a preferred embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted so as to avoid obscuring the subject matter of the present invention.

As used herein, the terms " about, " " substantially, " " etc. ", when used to refer to a manufacturing or material tolerance inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure.

The present invention relates to an underbody for a high rigidity vehicle, which is a structure in which a skin layer and a flame retardant layer are laminated, wherein the skin layer comprises thermoplastic fibers having a shape-retaining function; And PETG low melting point binder and having a weight ratio of 4: 6 to 9: 1, wherein the flame retardant layer is a reinforcing fiber; And a thermosetting binder containing a flame retardant. The weight ratio of the thermosetting binder is 100 to 10 to 50.

1 is a conceptual diagram of a highly rigid underbody section for a vehicle according to a preferred embodiment of the present invention, showing a structure in which a flame retardant layer 200 and a skin layer 100 are laminated.

More specifically, the skin layer is composed of fibers of two components, one of which is a nonwoven fabric having a shape-retaining function, and is made up of at least one or more fibers of polyester, polyimide, acrylic or nylon resin Thermoplastic fiber aggregate, and the other fiber is a low melting point binder, having a fineness of 2 to 15 denier and having a length of 10 to 80 mm.

The binder is preferably made of PETG (CHDM-modified polyethylene terephthalate) resin. PETG is a copolyester having a basic structure of terephthalic acid (TPA), ethylene glycol (EG) and CHDM (1,4-cyclohexanedimethanol) (glycol-modified poly (1,4-cyclohexylene dimethylene terephthalate) and has the following structural formula.

                          [constitutional formula]

The PETG resin has amorphous characteristics and can produce transparent products of all thicknesses that can be molded without whitening due to crystallization. In addition to its bright color and excellent gloss, it has excellent printability, impact resistance and chemical resistance. It can be processed in a wide range of conditions and its secondary processability is easy. Besides, it does not contain any environmental hormone substance, There is a feature that has environmental friendliness.

With these properties, PETG resins are now widely used in the fields of sheet, film, packaging materials, and molded products.

PETG is currently commercially produced from two companies in the world, Eastman Chemical Company of USA and SK Chemicals of Korea, and it is environmentally friendly and has excellent moldability, processability and transparency Lt; / RTI >

The PETG low melting point binder can be used as a sheath core composite fiber composed of PETG resin or a PETG resin single fiber.

Since PETG resin has no melting point and does not crystallize, it can be fused at 130 ~ 200 ℃, which is much lower than ordinary thermoplastic fibers. Especially, when molding process is done through strong pressure like underbody, The entire skin layer shows excellent rigidity.

The low-melting-point fiber used as the binder is in the form of a cisco-type, a polyester-based or nylon-based resin is used for the core portion, and a low melting point amorphous resin is used for the sheath portion. .

In this case, the resin used as the core part remains in the form of fiber without being melted even in the thermoforming. The reason why the low melting point resin is applied to only the sheath part is that the general melt spinning method It is very difficult to uniformly form the elongation, and even if the sacrifice is performed, it tends not to be focused upon carding, so that uniform mixing with other fibers is not achieved in the nonwoven fabric manufacturing process.

On the other hand, when PETG resin is used, the adhesiveness is not remarkably exhibited through the simple heat treatment. However, when thermoforming is performed under high pressure of 100 to 200 kgf / cm ² as in the underbody manufacturing process of an automobile, .

In addition, it offers uniform uniformity even if it is offered as a stand-alone card, not a Cisco cardinal, and it is not problematic in the carding process.

In addition, since all parts of the fiber are fused during thermoforming, they can contribute to better adhesion and strength compared to ordinary low melting point fibers at the same weight.

The thermoplastic fibers and binders of the shape-retaining function are formed by carding into a web and then needle-punched into a nonwoven fabric, wherein the weight ratio of thermoplastic fiber to PETG low melting point binder is 4: 6 to 9: 1.

The thermoplastic fiber of the shape-retaining function is a thermoplastic fiber aggregate composed of at least one fiber of a polyester-based, polyimide-based, acrylic and nylon resin, and generally has a melting point of 220 to 280 ° C. Therefore, when the skin layer composed of the thermoplastic fiber having the shape-maintaining function and the PETG low melting point binder is heated under the condition of not exceeding 220 캜 under the pressure heating, the PETG low melting point binder melts first and acts as an adhesive between the thermoplastic fibers having the shape- When pressed, it can be stuck more closely.

The flame-retardant layer is composed of a non-woven fabric through so-called super fibers having high heat resistance. A thermosetting binder is impregnated into the super fibers at 10 to 50 parts by weight with respect to 100 parts by weight of super fibers.

Wherein the superfine fiber is at least one selected from the group consisting of polyphenylene sulfide, polytetrafluoroethylene, polyimide, meta-aramid, para-aramid, polyarylate, polyparaphenylenebenzobisoxazole, 15 denier, and a length of 20 to 80 mm is preferably used.

The thermosetting binder is preferably composed of at least one selected from the group consisting of an epoxy-based resin and a phenol-based mixture. The thermosetting binder binds the superfine fibers and partially contains a flame retardant to maintain the shape of the flame retardant layer even at high temperatures.

The flame retardant is preferably composed of at least one selected from the group consisting of silicone, P / Br, zinc bromide, chlorine, phosphorus, and melamine compounds.

The skin layer and the flame-retardant layer may be fixed and fixed by a method such as needle punching, spun lace by water jet, stitch bonding, chemical bonding or the like, but they can be omitted if they can be sufficiently fixed by thermoforming. Therefore, a suitable bonding method can be used depending on the type of nonwoven fabric fibers and the manufacturing environment.

The chemical bonding may include a coating layer composed of one or more thermoplastic resins such as PVC, TPE, TPO, and an epoxy or phenolic adhesive.

Incorporating a tough laminate the lamination step into a mold the temperature of 200 ~ 220 ℃ holding press forming with a pressure of 120kgf / cm ² for 90 seconds in a mold preheating for 100 seconds, and the internal temperature is maintained to 240 ℃ straight Thereby producing an underbody having a thickness of about 10 mm.

It can be seen that the automobile underbody having excellent durability and excellent rigidity can be provided by the automobile underbody manufactured according to the embodiment of the present invention.

Hereinafter, the vehicle underbody according to the present invention will be described in detail with reference to examples and comparative examples. However, the following examples and comparative examples are only illustrative examples for explaining the present invention in more detail, and the present invention is not limited by the following examples and comparative examples. The method for measuring the physical properties by the underbody of a vehicle used in the following Examples and Comparative Examples is as follows.

* Tear strength measurement

A test piece was prepared and measured according to the method specified in ASTM D 1424. The tear test direction was in the MD (mechine direction) direction.

* Flexural strength and Flexural modulus  Measure

ASTM D790. ≪ / RTI >

Test specimen size is 50mm x 150mm, SPAN length is 100mm and SPAN and test specimen are in the center. At this time, the test speed is 5 mm / min, and the compressive load is applied on the surface layer of the test piece or the downward direction of the vehicle.

Example  One

The PET short fibers include 70 wt% and 30 wt% of the total nonwoven fabric weight, respectively, and the fineness of the PET staple fibers is 6 denier and has a fiber length of 51 mm. The fineness of the PETG fiber is 4 denier and has a fiber length of 51 mm. The skin layer is laminated at 600 gsm and is manufactured by a needle punching method.

≪ Flame Retardant Layer >: Polyphenylene sulfide short fibers form webs by carding method, and the fineness of the polyphenylene sulfide short fibers is 5 denier and has a fiber length of 51 mm. 450 gsm. The web was bonded by a needle punching method, and then a non-woven fabric was impregnated with a flame retardant resol type phenolic resin as a binder, followed by dehydration so that the phenol resin remained at 150 gsm.

The surface layer and the flame retardant layer were laminated, then charged into an underbody mold and thermoformed at a pressure of 120 kgf / cm 2 for 90 seconds at a temperature of 210 ° C to produce a highly rigid underbody for automobiles.

Comparative Example 1

Wherein the polyethylene terephthalate (PET) short fiber and the low melting point PET binder each comprise 70 wt% and 30 wt% of the total nonwoven fabric weight, the fineness of the PET staple fiber is 6 denier and has a fiber length of 51 mm, The melting point PET binder has a fineness of 4 denier and a fiber length of 51 mm.

The same as in Example 1 below.

Comparative Example 2

The PET staple fibers had a fineness of 6 denier and a fiber length of 51 mm and were laminated to have a surface density of 420 gsm, bound to the web by a needle punching method, and then lyzol-type phenol (polyethylene terephthalate The resin is impregnated with the nonwoven fabric, and then a dehydration process is performed so that a phenol resin is left at 180 gms, to produce a final flame retarding layer of 600 gsm. The same as in Example 1 below.

Example 1 Comparative Example 1 Comparative Example 2 Tensile Strength (MPa) 41.4 32.0 34.5 Tear strength (N) 340 160 220 Flexural Strength (N) 35.1 29.3 25.2 Flexural modulus (MPa) 477 442 415

As shown in Table 1, unlike Comparative Examples 1 and 2, Example 1 in which PETG fiber binders are mixed shows that tensile strength, flexural strength, and flexural modulus are improved by PETG fibers contained in the underbody can do. This is because the adhesiveness was improved as the PETG fiber was included. The improvement in adhesion can be confirmed by the difference in the tear strength value. Therefore, it is possible to provide a highly rigid underbody for a vehicle according to an embodiment of the present invention.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. It will be clear to those who have knowledge of.

100: skin layer 200: flame retardant layer

Claims (4)

In an underbody for a high rigidity vehicle,
A skin layer and a flame retardant layer are stacked,
Wherein the skin layer comprises thermoplastic fibers of a shape-retaining function; And PETG low melting point binder, and having a weight ratio of 4: 6 to 9: 1,
The PETG low melting point binder is a sheath core composite fiber composed of PETG resin with sheathing, which is a short fiber having a fiber elongation of 2 to 15 deniers and a fiber length of 10 to 80 mm,
The thermoplastic fiber of the shape-retaining function is composed of at least one or more fibers of a polyester-based, polyimide-based, acrylic and nylon resin,
Wherein the flame retardant layer comprises reinforcing fibers; And a thermosetting binder containing a flame retardant. The underbody is characterized by a weight ratio of 100 to 10 to 50.
delete delete The method according to claim 1,
Wherein the reinforcing fiber is a fiber composed of at least one of polyphenylene sulfide, polytetrafluoroethylene, polyimide, meta-aramid, para-aramid, polyarylate and polyparaphenylenebenzobisoxazole, Is a staple fiber having a length of 20 to 80 mm and a length of 2 to 15 denier.

Images